My 1970 Pi has developed a vibration through the body from the back end. It only occurs on left hand bends, when the suspension compresses on undulations in the road and when accelerating hard at speed.
About 2 months ago I fitted CV axles. There might have been a vibration then but I didn't get it out enough to really know. The front right diff mount was broken away and I probably assumed any problems were associated with that.
Last week I had the diff mounts repaired and strengthened by a Triumph specialist garage, He also put a new pinion seal in as the old one had a slight weep.
The car had rear telescopic shocks twhich were attached to the body on the wheel arch. I bought new mounts and shocks from the Triumph man and when I got it home I fitted them. I drove the car on a few 10 km local runs and was happy with it in suburban driving.
Yesterday I took her on a weekend TR Register run to test out the changes.
On the freeway at 110-120 km/h the vibrations from the rear end were concerning. Again, they only occur on left hand bends, when the suspension compressed on undulations in the road and when accelerating hard at speed. In a straight line and on right hand bends the car was vibration free at all speeds. There are no noises associated with the vibrations.
At a meeting with other cars 100kms from home I noticed a pool of oil under the car. A quick look and it was from the new pinion seal. While we were stopped I gave the rear end a bounce and it was obvious the new adjustable shocks were set too soft. As we were heading to a remote spot I decided to take the car home and join the others at our destination in another car.
On the run home I took it easy due to the oil leak, 70-90km/h. The vibration was no worse or better than before. Again, in a straight line or on right hand bends it was vibration free. Near home I gave her a burst in 2nd and there wasn't a noticeable problem.
I am assuming the leak and vibration were unrelated, there is no sign the pinion bearing has a problem and I am confident the garage would have picked any problem up when replacing the seal. I could be wrong.
My suspicions were that the vibration was caused by:
- The body flexing enough on bends and when the suspension compressed to touch the new shock mounts. The new mounts are only a few mm clear of one now superfluous bolt that held the old body mount on. If the body flexed on corners, under acceleration or on undulations in the road the body might touch the shock mount transmitting road wheel vibration through the body. Only really noticeable at speed due to the increased vibration from the wheels.
- The soft rear shocks were exacerbating the problem.
- A bad diff pinion or axle bearing. I doubt this as a bearing problem would be there all the time, make a noise and get worse as time went on.
- A defective CV axle. I don't know enough how these axles work to know whether a CV axle would induce vibration only in the situations they were occurring.
Any ideas thank you all? I will remove the offending bolts that are close to the new mounts but others may have experienced similar vibrations and it would be great to have other possibilities to look at while it is apart.